Mobile plating system and method

ABSTRACT

An exemplary mobile plating system is provided for performing a plating process using virtually any known or available deposition technology for coating or plating as substrate. The mobile plating system may include a vacuum chamber positioned in a mobile storage volume, an external vacuum pump, and a control circuitry to control the operation of some or all of the operations of the external vacuum pump. The external vacuum pump is positioned in the mobile storage volume when the mobile plating system is in transit, and is positioned external to the mobile storage volume when the mobile plating system is stationary and in operation. The external vacuum pump may be mounted on a skid, and, in operation, the external vacuum pump couples with the vacuum chamber to assist with producing a desired pressure in the vacuum chamber. The external vacuum pump couples with the vacuum chamber using a flexible piping segment and/or dampening arrangement to reduce and/or eliminate any mechanical vibrations within the vacuum chamber and within the mobile storage volume due to the operation of the external vacuum pump.

RELATED APPLICATIONS

[0001] Pursuant to 35 U.S.C. §120, this continuation application claimspriority from, and hereby incorporates by reference for all purposes,copending U.S. patent application Ser. No. 09/576,640, entitled MobilePlating System and Method, naming Jerry D. Kidd, Craig D. Harrington,and Daniel N. Hopkins as inventors, filed May 22, 2000. This applicationdoes not claim priority from but is related to U.S. patent applicationSer. No. 09/427,775 entitled System and Method for Plasma Plating, filedOct. 26, 1999, and named Jerry D. Kidd, Craig D. Harrington, and DanielN. Hopkins as joint inventors, and U.S. patent application Ser. No.09/578,166, entitled Configurable Vacuum System and Method, filed May22, 2000, and named Jerry D. Kidd, Craig D. Harrington, and Daniel N.Hopkins as joint inventors.

TECHNICAL FIELD OF THE INVENTION

[0002] This invention relates in general to the field of mobile systemsand deposition technology for plating and coating materials and moreparticularly to a mobile plating system and method.

BACKGROUND OF THE INVENTION

[0003] Deposition technologies for coating and plating materials anddeveloping engineered surfaces may include any of a variety ofdeposition technologies. These deposition technologies may include, forexample, vacuum deposition or physical vapor deposition (“PVD”),chemical vapor deposition (“CVD”), sputtering, and ion plating.Generally, these deposition technologies may involve the steps of: (a)preparing and cleaning the surface of the target or substrate; (b)establishing a vacuum or desired pressure level at designated operatingparameters; and (c) performing the deposition. Such depositiontechnologies involve large, expensive, and complex systems, equipment,and machinery.

[0004] For example, many such deposition technologies require anexpensive, bulky, and complex vacuum system to establish and maintain avacuum at a designated operating pressure. Such a vacuum system mayinclude, generally, a vacuum chamber, mechanical vacuum pumps, which maybe used as roughing and foreline vacuum pumps, a secondary vacuum pump,such as a diffusion pump, a cryo pump, and/or a turbo molecular pump,and complex pressure gauges, such as an ion vacuum gauge. These vacuumsystems often require complex piping and plumbing configurations thatmust be free of leaks so that the precise and desired operatingpressures and parameters can be maintained and followed. Such complexpiping and plumbing is particularly subject to leakage at turns in thepipes or joints where pipes interface due to interface problems andmechanical vibrations caused by the operation of the vacuum pumps.

[0005] Some or all of the vacuum pumps, such as a diffusion pump, mayalso require a large and complex cooling system that, often, useshundreds or thousands of gallons of water that must be cooled andcirculated prior and during the operation of the vacuum pump. This mayrequire a large and bulky water cooling system that includes a largewater storage tank and a refrigeration system to cool the water in thelarge storage tank.

[0006] Because deposition technologies involve such large, expensive,and complex systems, equipment, and machinery, such systems must,generally, be permanently installed at a location. When large parts orcomponents, such as those weighing hundreds or thousands of pounds, orwhen bulky or hard to ship parts or components need to be coated orplated using one of the deposition technologies, about the only optionis to permanently install such a system at or near such large or bulkycomponents. This allows such large and bulky components to be moved onlya short distance to be coated or plated.

[0007] Unfortunately, because this is such an expensive option, it isoften cost prohibitive. The high expenses include, not only the cost inprocuring the real estate and equipment, and in setting up such complexsystems, but in maintaining the equipment and in hiring and employingpersonnel with the special expertise needed to successfully operate andmaintain such systems. Problems also exist in designing a depositiontechnology system. All such systems require custom design work to meetthe particular needs and circumstances of the installation. Turnkeydeposition technology systems simply do not exist. As has beenillustrated, the design, installation, operation, and maintenance ofdeposition technology systems are complex and expensive, and, as aresult, the coating or plating of large and bulky components usingdeposition technologies is often not available, even though such largeand bulky components may greatly benefit from the significant advantagesoffered by such deposition technologies.

[0008] In some cases, the availability of certain components or parts isso critical that, from either a safety and/or a financial standpoint,the risk of a shipping delay or lost shipment, no matter how small, istoo great a risk to take, even if significant advantages could be gainedthrough coating or plating. For example, a reactor vessel head stud thatis used in a nuclear power plant is so crucial and unique, that the riskof a shipping delay or lost shipment during a plant outage, such as, forexample, during a fuel reload at a nuclear power plant that occurs everycouple of years or so, is too great to take. For example, for every daythat a nuclear plant is kept off line because of a delay, hundreds ofthousands or even millions of dollars may be lost. Thus, certaincomponents or parts are so crucial that they would never be shipped toanother location for plating or coating using deposition technologies,in spite of all of the significant advantages that may be realizedthrough such deposition technologies.

SUMMARY OF THE INVENTION

[0009] From the foregoing it may be appreciated that a need has arisenfor a mobile plating system and method that allows a plating system,including all associated sophisticated equipment and system to beconveniently provided at a user's location or virtually any desiredlocation. In accordance with the present invention, a mobile platingsystem and method are provided that substantially eliminate one or moreof the disadvantages and problems outlined above.

[0010] According to an aspect of the present invention, a mobile platingsystem for performing a plating process is provided. The mobile platingsystem includes a vacuum chamber positioned in a mobile storage volume,an external vacuum pump, and a control circuitry to control theoperation of some or, in other embodiments, all of the operations of theexternal vacuum pump. The external vacuum pump is positioned in themobile storage volume when the mobile plating system is in transit, andis positioned external to the mobile storage volume when the mobileplating system is stationary and in operation. The external vacuum pumpmay be mounted on a skid, and, in operation, the external vacuum pumpcouples with the vacuum chamber to assist with producing a desiredpressure in the vacuum chamber. The external vacuum pump couples withthe vacuum chamber using a flexible piping segment and/or dampeningarrangement to reduce and/or eliminate any mechanical vibrations causedby the operation of the external vacuum pump. The vacuum chamber has aninternal volume large enough to contain a substrate to be plated that isthe size of at least one reactor vessel head stud. This provides a largeenough volume to plate substrates or parts that are either large orsmall.

[0011] The present invention provides a profusion of technicaladvantages that include the capability to locate sophisticateddeposition technologies, systems, equipment, and machinery for coatingand plating at virtually any desired location, which substantiallyincreases the availability of such important technology.

[0012] Another technical advantage of the present invention includes thecapability to make coating or plating from deposition technologiesavailable for large and bulky components and parts that cannot beshipped or cannot be easily shipped without having to incur thesignificant expense of designing, operating, and maintaining a complexsystem using deposition technology.

[0013] Yet another technical advantage of the present invention includesthe capability to coat or plate mission critical components, such asreactor vessel head studs used at nuclear power plants. Because thepresent invention allows deposition technologies to be brought to thecustomer, unacceptable risks due to possible shipping delays or lostshipments are eliminated.

[0014] Another technical advantage of the present invention includes thecapability to reduce or eliminate shipping costs, even for smallercomponents and parts or non-mission critical parts, and eliminate theneed to incur the substantial expense and cost of designing, operating,and maintaining a complex system using deposition technology. Thissignificantly reduces overall costs.

[0015] Still yet another technical advantage of the present inventionincludes the capability to operate noisy mechanical vacuum pumps, suchas mechanical roughing and foreline pumps, external to the mobilechamber resulting in reduced mechanical vibrations and increasedoperational reliability of the mobile plating system.

[0016] Still yet another technical advantage includes the capability touse sophisticated cooling system, such as a water cooling system, withina mobile storage volume of the mobile plating system.

[0017] Yet another technical advantage includes the capability to usesophisticated deposition technology without producing or leaving behindany harmful waste byproducts. This is significant.

[0018] Other technical advantages are readily apparent to one skilled inthe art from the following figures, description, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] For a more complete understanding of the present invention andthe advantages thereof, reference is now made to the following briefdescription, taken in connection with the accompanying drawings anddetailed description, wherein like reference numerals represent likeparts, in which:

[0020]FIG. 1 is a schematic diagram that illustrates a system for plasmaplating that can be used to plate materials, according to an embodimentof the present invention;

[0021]FIG. 2 is a top view of a vacuum chamber of a system for plasmaplating that illustrates one embodiment of a platform implemented as aturntable;

[0022]FIG. 3 is a side view that illustrates the formation anddispersion of a plasma around a filament to plasma plate a substrateaccording to an embodiment of the present invention;

[0023]FIG. 4 is a sectional view that illustrates a deposition layerthat includes a base layer, a transition layer, and a working layer;

[0024]FIG. 5 is a flowchart that illustrates a method for plasma platingaccording to an embodiment of the present invention;

[0025]FIG. 6 is a flowchart that illustrates a method for backsputteringusing the system of the present invention, according to an embodiment ofthe present invention;

[0026]FIG. 7 is a top view of a mobile plating system according to oneembodiment of the present invention;

[0027]FIG. 8 is a side view of a connection of an external vacuum pumpto a vacuum chamber of the mobile plating system; and

[0028]FIG. 9 is a flowchart that illustrates a method for using a mobileplating system according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0029] It should be understood at the outset that although an exemplaryimplementation of the present invention is illustrated below, thepresent invention may be implemented using any number of techniques,whether currently known or in existence. The present invention should inno way be limited to the exemplary implementations, drawings, andtechniques illustrated below, including the exemplary design andimplementation illustrated and described herein.

[0030] Initially, a system and method for plasma plating is described indetail below in connection with FIGS. 1-6 to illustrate a type ofdeposition technology that may be used with the mobile plating systemand method. Although it should be understood that the present inventionis in now way limited to the exemplary plating or deposition technologyillustrated and discussed in connection with FIGS. 1-6, and that thepresent invention may be used with virtually any known or availableplating or deposition technique. Finally, an embodiment of the mobileplating system and method are described in detail in connection withFIGS. 7-9 that implements, as an example, the plasma plating system typeof deposition technology detailed previously in connection with FIGS.1-6.

[0031]FIG. 1 is a schematic diagram that illustrates a system 10 forplasma plating that can be used to plate any of a variety of materials,according to an embodiment of the present invention. The system 10includes various equipment used to support the plasma plating of asubstrate 12 within a vacuum chamber 14. Once appropriate operatingparameters and conditions are achieved, a depositant provided in afilament 16 and a filament 18 may be evaporated or vaporized to form aplasma. The plasma will contain, generally, positively charged ions fromthe depositant and will be attracted to the substrate 12 where they willform a deposition layer. The plasma may be thought of as a cloud of ionsthat surround or are located near the substrate 12. The plasma willgenerally develop a dark region, near the closest surface of thesubstrate 12 from the filament 16 and the filament 18, that providesacceleration of the positive ions to the substrate 12.

[0032] The filament 16 and the filament 18 reside within the vacuumchamber 14 along with a platform 20, which supports the substrate 12. Adrive assembly 22 is shown coupled between a drive motor 24 and a mainshaft of the platform 20 within the vacuum chamber 14. In the embodimentshown in FIG. 1, the platform 20 is provided as a turntable that rotateswithin the vacuum chamber 14. The drive assembly 22 mechanically linksthe rotational motion of the drive motor 24 with the main shaft of theplatform 20 to impart rotation to the platform 20. The rotation of themain shaft of the platform 20 is enhanced through various supportbearings such as a base plate bearing 28 and a platform bearing 30.

[0033] As is illustrated, the vacuum chamber 14 resides or is sealed ona base plate 32. The vacuum chamber 14 may be provided using virtuallyany material that provides the appropriate mechanical characteristics towithstand an internal vacuum and an external pressure, such asatmospheric pressure. For example, the vacuum chamber 14 may be providedas a metal chamber or as a glass bell. In an alternative embodiment, thebase plate 32 serves as the platform 20 to support the substrate 12. Thebase plate 32 may be thought of as part of the vacuum chamber 14.

[0034] The base plate 32 also provides mechanical support for the system10 while allowing various devices to feed through from its bottomsurface to its top surface within the vacuum chamber 14. For example,the filament 16 and the filament 18 receive power from a filament powercontrol module 34. It should be noted that although two filament powercontrol modules 34 are shown in FIG. 1, preferably, these two modulesare implemented as one module. In order to provide power to the filament16 and the filament 18, electrical leads must feed through the baseplate 32 as illustrated in FIG. 1. Similarly, the drive motor 24 mustalso penetrate or feed through the base plate 32 to provide mechanicalaction to the drive assembly 22 so that the platform 20 may be rotated.The electrical feed through 26, described more fully below, also feedsthrough the base plate 32 and provides an electrical conductive pathbetween the platform 20 and various signal generators, also describedmore fully below. In a preferred embodiment, the electrical feed through26 is provided as a commutator that contacts the bottom surface of theplatform 20, in the embodiment where the platform 20 is implemented as aturntable. The electrical feed through 26 may be implemented as acommutator and may be implemented as a metal brush which can contact thebottom surface of the platform 20 and maintain an electrical contacteven if the platform 20 rotates.

[0035] The filament power control module 34 provides an electric currentto the filament 16 and the filament 18. In one embodiment, the filamentpower control module 34 can provide current to the filament 16 for aparticular duration, and then provide current to the filament 18 duringa second duration. Depending upon how the filaments are configured, thefilament power control module 34 may provide current to both thefilament 16 and the filament 18 at the same time or during separateintervals. This flexibility allows more than one particular depositantmaterial to be plasma plated onto the substrate 12 at different times.The filament power control module 34 preferably provides alternatingcurrent to the filaments, but may provide a current using any knownmethod of generating current. In a preferred embodiment, the filamentpower control module 34 provides current at an amplitude or magnitudethat is sufficient to generate enough heat in the filament 16 toevaporate or vaporize the depositant provided therein.

[0036] In order to ensure even heating of the depositant, which will beprovided at or in the filament 16 or the filament 18, the currentprovided by the filament control module 34 will preferably be providedusing incremental staging so that a more even heat distribution willoccur in the depositant that is being melted within the vacuum chamber14.

[0037] In a preferred embodiment, the platform 20 is implemented as aturntable and rotates using the mechanical linkage as described above. Aspeed control module 36, as shown in FIG. 1, may be provided to controlthe speed of the rotation of the platform 20. Preferably, the rotationof the platform 20 occurs at a rate from five revolutions per minutes to30 revolutions per minute. It is believed that an optimal rotationalrate of the platform 20 for plasma plating is provided at a rotationalrate of 12 revolutions per minute to 15 revolutions per minute. Theadvantages of rotating the platform 20 are that the substrate 12 can bemore evenly plated or coated. This is especially true when multiplesubstrates are provided on the surface of the platform 20. This allowseach one of the multiple substrates to be similarly positioned, onaverage, within the vacuum chamber 14 during the plasma plating process.

[0038] In other embodiments, the platform 20 may be provided atvirtually any desired angle or inclination. For example, the platform 20may be provided as a flat surface, a horizontal surface, a verticalsurface, an inclined surface, a curved surface, a curvilinear surface, ahelical surface, or as part of the vacuum chamber such as a supportstructure provided within the vacuum chamber. As mentioned previously,the platform 20 may be stationary or rotate. In an alternativeembodiment, the platform 20 includes rollers that may be used to rotateone or more substrates.

[0039] The platform 20, in a preferred embodiment, provides or includesan electrically conductive path to provide a path between the electricalfeed through 26 and the substrate 12. In one embodiment, platform 20 isprovided as a metal or electrically conductive material such that anelectrically conductive path is provided at any location on the platform20 between the electrical feed through 26 and the substrate 12. In suchas a case, an insulator 21, will be positioned between the platform 20and the shaft that rotates the platform 20 to provide electricalisolation. In another embodiment, the platform 20 includes electricallyconductive material at certain locations on its top surface thatelectrically coupled to certain locations on the bottom surface. In thismanner, the substrate 12 can be placed at an appropriate location on thetop side of the platform 20 while the electrical feed through 26 may bepositioned or placed at an appropriate location on the bottom side ofthe platform 20. In this manner, the substrate 12 is electricallycoupled to the electrical feed through 26.

[0040] The electrical feed through 26 provides a dc signal and a radiofrequency signal to the platform 20 and the substrate 12. The desiredoperational parameters associated with each of these signals aredescribed more fully below. Preferably, the dc signal is generated by adc power supply 66 at a negative voltage and the radio frequency signalis generated by an rf transmitter 64 at a desired power level. The twosignals are then preferably mixed at a dc/rf mixer 68 and provided tothe electrical feed through 26 through an rf balancing network 70, whichprovides signal balancing by minimizing the standing wave reflectedpower. The rf balancing network 70 is preferably controlled through amanual control.

[0041] In an alternative embodiment, the platform 20 is eliminated,including all of the supporting hardware, structures, and equipment,such as, for example, the drive motor 24, and the drive assembly 22. Insuch a case the substrate 12 is electrically coupled to the electricalfeed through 26.

[0042] The remaining equipment and components of the system 10 of FIG. 1are used to create, maintain, and control the desired vacuum conditionwithin the vacuum chamber 14. This is achieved through the use of avacuum system. The vacuum system includes a roughing pump 46 and aroughing valve 48 that is used to initially pull down the pressure inthe vacuum chamber 14. The vacuum system also includes a foreline pump40, a foreline valve 44, a diffusion pump 42, and a main valve 50. Theforeline valve 44 is opened so that the foreline pump 40 can began tofunction. After the diffusion pump 42 is warmed or heated to anappropriate level, the main valve 50 is opened, after the roughing pump46 has been shut in by closing the roughing valve 48. This allows thediffusion pump 42 to further reduce the pressure in the vacuum chamber14 below a desired level.

[0043] A gas 60, such as argon, may then be introduced into the vacuumchamber 14 at a desired rate to raise the pressure in the vacuum chamber14 to a desired pressure or to within a range of pressures. A gascontrol valve controls the rate of the flow of the gas 60 into thevacuum chamber 14 through the base plate 32.

[0044] Once all of the operating parameters and conditions areestablished, as will be described more fully below in connection withFIGS. 5 and 6 according to the teachings of the present invention,plasma plating occurs in system 10. The substrate 12 may be plasmaplated with a deposited layer, which may include one or more layers suchas a base layer, a transitional layer, and a working layer, through theformation of a plasma within the vacuum chamber 14. The plasma willpreferably include positively charged depositant ions from theevaporated or vaporized depositant along with positively charged ionsfrom the gas 60 that has been introduced within the vacuum chamber 14.It is believed, that the presence of the gas ions, such as argon ions,within the plasma and ultimately as part of the depositant layer, willnot significantly or substantially degrade the properties of thedepositant layer. The introduction of the gas into the vacuum chamber 14is also useful in controlling the desired pressure within the vacuumchamber 14 so that a plasma may be generated according to the teachingsof the present invention. In an alternative embodiment, the plasmaplating process is achieved in a gasless environment such that thepressure within the vacuum chamber 14 is created and sufficientlymaintained through a vacuum system.

[0045] The generation of the plasma within the vacuum chamber 14 isbelieved to be the result of various contributing factors such asthermionic effect from the heating of the depositant within thefilaments, such as the filament 16 and the filament 18, and theapplication of the dc signal and the radio frequency signal at desiredvoltage and power levels, respectively.

[0046] The vacuum system of the system 10 may include any of a varietyof vacuum systems such as a diffusion pump, a foreline pump, a roughingpump, a cryro pump, a turbo pump, and any other pump operable or capableof achieving pressures within the vacuum chamber 14 according to theteachings of the present invention.

[0047] As described above, the vacuum system includes the roughing pump46 and the diffusion pump 42, which is used with the foreline pump 40.The roughing pump 46 couples to the vacuum chamber 14 through theroughing valve 48. When the roughing valve 48 is open, the roughing pump46 may be used to initially reduce the pressure within the vacuumchamber 14. Once a desired lower pressure is achieved within the vacuumchamber 14, the roughing valve 48 is closed. The roughing pump 46couples to the vacuum chamber 14 through a hole or opening through thebase plate 32. The roughing pump 46 will preferably be provided as amechanical pump. In a preferred embodiment of the vacuum system of thesystem 10 as shown in FIG. 1, the vacuum system in this embodiment alsoincludes a foreline pump 40 coupled to a diffusion pump 42 through aforeline valve 44. The foreline pump 40 may be implemented as amechanical pump that is used in combination with the diffusion pump 42to reduce the pressure within the vacuum chamber 14 to a level evenlower than that which was produced through the use of the roughing pump46.

[0048] After the roughing pump 46 has reduced the pressure within thevacuum chamber 14, the diffusion pump 42, which uses heaters and mayrequire the use of cooling water or some other substance to cool thediffusion pump 42, couples with the vacuum chamber 14 through a mainvalve 50 and through various holes or openings through the base plate 32as indicated in FIG. 1 by the dashed lines above the main valve 50 andbelow the platform 20. Once the diffusion pump 42 has been heated up andmade ready for operation, the main valve 50 may be opened so that thepressure within the vacuum chamber 14 may be further reduced through theaction of the diffusion pump 42 in combination with the foreline pump44. For example, the pressure within the vacuum chamber 14 may bebrought below 4 milliTorr. During a backsputtering process, the pressurein the vacuum chamber 14 may be dropped to a level at or below 100milliTorr on down to 20 milliTorr. Preferably, the pressure within thevacuum chamber 14 during a backsputtering process will be at a level ator below 50 milliTorr on down to 30 milliTorr. During normal operationof the system 10 during a plasma plating process, the pressure withinthe vacuum chamber 14 may be reduced by the vacuum system to a level ator below 4 milliTorr on down to a value of 0.1 milliTorr. Preferably,the vacuum system will be used during a plasma plating process to reducethe pressure within the vacuum chamber 14 to a level at or below 1.5milliTorr on down to 0.5 milliTorr.

[0049]FIG. 2 is a top view of a vacuum chamber of a system for plasmaplating that illustrates one embodiment of a platform implemented as aturntable 20. The turntable 20 is shown with substrates 12 a, 12 b, 12c, and 12 d positioned, symmetrically on the surface of the turntable20. The turntable 20 may rotate either clockwise or counterclockwise.The substrates 12 a-12 d may be virtually any available material and areshown in FIG. 2 as round, cylindrical components such that the top viewof each of the substrates presents a circular form.

[0050] The filament power control module 34 is electrically coupled to afirst set of filaments 94 and 96 and a second set of filaments 90 and92. Although the electrical connections are not fully illustrated inFIG. 2, it should be understood that the filament power control module34 may supply current to the first set of filaments 94 and 96 or to thesecond set of filaments 90 and 92. In this manner, the deposition layermay be provided with two sublayers such as a base layer and a workinglayer. The base layer will preferably be applied first throughdepositants provided in the first set of filaments 94 and 96 while theworking layer will be deposited on the base layer of the substrates 12a-12 d using the depositants provided at the second set of filaments 90and 92.

[0051] The arrangement of the substrates in FIG. 2 may be described asan array of substrates that include inwardly facing surfaces, which arecloser to the center of the turntable 20, and outwardly facing surfaces,which are closer to the outer edge of the turntable 20. For example, theinwardly facing surfaces of the array of substrates 12 a-d will bepresented to the filament 92 and the filament 96, at different times ofcourse, as they are rotated near the filaments. Similarly, the outwardlyfacing surfaces of the substrates 12 a-d will be presented to thefilaments 90 and 94 as they rotate near these filaments.

[0052] As mentioned previously, the filament power control module 34 mayprovide a current in virtually any form, such as a direct current or analternating current, but preferably provides current as an alternatingcurrent.

[0053] In operation, turntable 20 rotates, for example, in a clockwisedirection such that after substrate 12 b passes near or through thefilaments, the next substrate that will pass near or through thefilaments is substrate 12 c, and so on. In one example, the first set offilaments 94 and 96 are loaded with a depositant, such as nickel (ortitanium), and the second set of filaments are loaded with a depositantsuch as the metal alloy silver\palladium. This example illustrates a twoshot application or a two layer deposition layer.

[0054] After all of the operating parameters have been establishedwithin the vacuum chamber, as described throughout herein, the filamentpower control module 34 may energize or provide alternating current tothe first set of filaments 94 and 96 so that the nickel will evaporateor vaporize to form a plasma with the gas, such as argon gas, within thevacuum chamber. The positively charged nickel ions and the positivelycharged argon ions in the plasma will be attracted to the substrates 12a-d, which are at a negative potential. Generally, the closer thesubstrate is to the first set of filaments 90 and 92 as it rotates, themore material will be deposited. Because the turntable is rotating, auniform or more even layer will be applied to the various substrates.

[0055] After the first plasma has been plated onto the array ofsubstrates 12 a-d to form a base layer of the depositant layer on thesubstrates, the filament power control module 34 is energized so that asufficient amount of current is provided to the second set of filaments90 and 92. Similarly, a plasma is formed between the argon ions and thesilver\palladium ions and the working layer is then formed to thesubstrates that are being rotated.

[0056] During the first shot when the base layer is being applied, theoutwardly facing surfaces of substrates 12 a-d are primarily coatedthrough the nickel depositant located in the filament 94. Similarly, theinwardly facing surfaces of the substrates are coated by the nickeldepositant located in the filament 96. The same relation holds true forthe second shot where the silver\palladium is plasma plated onto thesubstrates to form the deposit layer.

[0057]FIG. 3 is a side view that illustrates the formation anddispersion of a plasma around a filament 100 to plasma plate a substrate12 according to an embodiment of the present invention. The filament 100is implemented as a wire basket, such as tungsten wire basket, and isshown with a depositant 102 located within, and mechanically supportedby, the filament 100. As the filament power control module 34 providessufficient current to the filament 100, the depositant 102 melts orvaporizes and a plasma 104 is formed. Of course, all of the operatingparameters of the present invention must be present in order to achievethe plasma state so that plasma plating may take place.

[0058] The substrate 12, which is provided at a negative potential,attracts the positive ions of the plasma 104 to form a deposition layer.As is illustrated, the dispersion pattern of the plasma 104 results inmost of the positive ions of the plasma 104 being attracted to the sideadjacent or nearest to the filament 100 and the depositant 102. Somewrap around will occur such as that illustrated by the plasma 104contacting the top surface of the substrate 12. Similarly, some of thepositive ions of the plasma 104 may be attracted to the platform orturntable. As is illustrated, the present invention provides anefficient solution for the creation of a deposition layer by ensuringthat most of the ions from the depositant are used in the formation ofthe deposition layer.

[0059]FIG. 4 is a sectional view that illustrates a deposition layer ofthe substrate 12 that includes a base layer 110, a transition layer 112,and a working layer 114. It should be noted at the outset that thethickness of the various layers that form the deposition layer aregrossly out of proportion with the size of the substrate 12; however,the relative thicknesses of the various sublayers or layers of thedeposition layer are proportionate to one another, according to oneembodiment of the present invention.

[0060] Generally, the thickness of the entire deposition layer on thesubstrate, according to the teachings of the present invention, arebelieved to generally range between 500 and 20,000 Angstroms. In apreferred embodiment, the entire thickness of the deposition layer isbelieved to range between 3,000 and 10,000 Angstroms. The presentinvention provides excellent repeatability and controllability ofdeposition layer thicknesses, including all of the sublayers such as thebase layer 110, the transition layer 112, and the working layer 114. Itis believed that the present invention can provide a controllable layerthickness at an acuracy of around 500 Angstroms. It should also bementioned that the present invention may be used to form a depositionlayer with one or any multiple of sublayers.

[0061] The thickness of the deposition layer is normally determinedbased on the nature of intended use of the plasma plated substrate. Thismay include such variables as the temperature, pressure, and humidity ofthe operating environment, among many other variables and factors. Theselection of the desired metal or depositant type for each layer is alsohighly dependent upon the nature of the intended use of the plasmaplated substrate.

[0062] For example, the present invention prevents or substantiallyreduces galling or mating or interlocking components. Galling includesthe seizure of mated components that often occur when two surfaces, suchas threaded surfaces, are loaded together. Galling can cause componentsto fracture and break, which often results in severe damage. Plasmaplating may be used to prevent or reduce galling by plating one or morecontacting surfaces.

[0063] Various depositants may be used to achieve this beneficialeffect. It is believed, however, that galling is preferably reducedthrough a plasma plating process that deposits a base layer of nickel ortitanium and a working layer of a silver/palladium metal alloy on one ormore contacting surfaces. For high temperature applications, such asover 650 degrees Fahrenheit, it is believed that the galling ispreferably reduced through a plasma plating process that deposits anickel or titanium base layer and a working layer of gold.

[0064] It has been found through experimentation that chromium does notwork well to reduce galling, this includes when the chromium isdeposited as either the base layer, the transition layer, or the workinglayer. It is believed that chromium may be a depositant that is moredifficult to control during the plasma plating process.

[0065] Plasma plating may also be used to plate valve parts, such asvalve stems in nonnuclear applications, and are preferably plasma platedusing a titanium base layer, a gold transition layer, and an indiumworking layer. In nuclear applications, such as nuclear power plantapplications, indium is not a preferred plasma plating depositantbecause it is considered to be too much of a radioactive isotopeabsorber. Instead, valve stems in nuclear applications are preferablyplasma plated using a nickel base layer and a silver/palladium metalalloy working layer.

[0066] As is illustrated in FIG. 4, the working layer 14 is normallyprovided at a substantially larger thickness than the correspondingtransition layer 112 and the base layer 110. It should also be notedthat the coating of the top of the substrate 12 is shown to be thin ator near the center or middle of the substrate 12. This effect is due tohow the filaments are positioned during the plasma plating process. Forexample, if the filaments are positioned similarly to that illustratedin FIGS. 2-3, the middle or center portion of the substrate 12 willgenerally have a thinner overall profile than the side of the depositionlayer.

[0067] Although various ranges of thicknesses have been discussedherein, it should be understood that the present invention is notlimited to any maximum deposition layer thickness. The thickness of thedeposition layer, especially the thickness of the working layer 114, canbe provided at virtually any desired thickness, normally depending uponthe operating environment in which the plasma plated substrate 12 willbe introduced. The base layer 110 and the transition layer 112 and anyother layers below the working layer 114 will preferably be provided ata substantially smaller thickness than the corresponding thickness ofthe working layer 114. For example, the base layer 110 and thetransition layer 112 may be provided at a thickness ranging from 500 to750 Angstroms while the working layer 114 may be provided at virtuallyany thickness such as for example 18,000 Angstroms.

[0068]FIG. 5 is a flow chart of a method 500 for plasma platingaccording to an embodiment of the present invention. The method 500begins at block 502 and proceeds to block 504. At block 504, thematerial or substrate that will be plasma plated is prepared for theprocess. This may include cleaning the substrate to remove any foreignmaterials, contaminants, and oils. Any of a variety of known cleaningprocesses may be used such as those defined by the Steel StructuresPainting Council (SSPC). For example, the SSPC-5 standard may beemployed to ensure that a substrate is cleaned to a white metalcondition. Similarly, the SSPC-10 standard may be employed. Preferably,the substrate will undergo an abrasive blasting, such as for example,bead blasting to further ensure that any foreign materials orcontaminants are removed. It should be noted that an oxidation layer maybe present on the surface of the substrate. The present invention allowsfor a deposition layer to be plasma plated onto the substrate surface,even in the presence of an oxidation layer, with excellent adhesion andmechanical properties.

[0069] The method 500 proceeds next to block 506 where the plasmaplating system prerequisites are established. Depending upon theimplementation of the system for plasma plating, this may involve any ofa variety of items. In the situation where a diffusion pump is used aspart of the vacuum system, items such as the availability of coolingwater must be established. Similarly, the adequate availability of lubeoil and air to operate the various equipment, valves, and machineryassociated with the system for plasma plating must be established. Anadequate supply of gas, such as argon gas, should also be verified andchecked at this point before proceeding to block 510.

[0070] At block 510, assuming that a diffusion pump is used as part ofthe vacuum system, the diffusion pump is prepared for operation. Thismay include opening a foreline valve and the starting of the forelinevacuum pump which is used in combination with the diffusion pump. Once aforeline vacuum has been drawn, the heaters of the diffusion pump may beenergized. This places the diffusion pump in service.

[0071] The method 500 proceeds next to block 512 where the vacuumchamber is set up. This includes any number of processes such aspositioning the substrate within the vacuum chamber. This is normallyachieved by positioning or placing the substrate at a specified locationon a platform or turntable located within the vacuum chamber. Beforeaccessing the internal volume of the vacuum chamber, the vacuum chamberseal must be broken and the bell jar or outer member is preferablylifted away from its base plate. Once the substrate is positioned on theplatform, the filaments may be positioned relative to the placement ofthe substrate.

[0072] The positioning of the filaments may involve any number oftechniques and includes such variables as the amount and type ofdepositant to be provided at the filament, and the distance, not onlyrelative to the substrate, but relative to other filaments. Generally,the filament will be located a distance ranging from 0.1 inches to 6inches from the substrate, as measured from the center line of thefilament, or from the depositant, to the closest point of the substrate.Preferably, however, the distance between the filament or the depositantand the substrate will range anywhere from 2.75 inches to 3.25 incheswhen the depositant will serve as the base layer or transition layer ofthe deposition layer. Similarly, when the depositant will serve as theworking layer of the deposition layer that will be deposited on thesubstrate, the distance between the filament or the depositant and thesubstrate is preferably provided at a distance between 2 inches and 2.5inches.

[0073] In the situation where multiple depositants or multiple shotswill be performed in the plasma plating process, it is necessary toconsider the placement of the filaments that will hold the firstdepositant relative to those that will hold the second depositant aswell as each of the filament's position relative to each other and thesubstrate. Generally the distance of a second filament from a firstfilament, which will include a depositant that will serve as a baselayer, transition layer, or a working layer of a deposition layer,should be anywhere between 0.1 inches and 6 inches.

[0074] The spacing between filaments that include depositants that willserve as a base layer, is generally provided between 0.1 inches and 6inches. Preferably, this distance shall be between 3 inches and 4inches. The foregoing filament spacing information also applies when thedepositant provided in the filaments will serve as the transition layerin the deposition layer. Similarly, the spacing between filaments, whichinclude a depositant that will serve as the working layer of thedeposition layer, should generally be between 0.1 inches and 6 inches,but, preferably, will be between 2.5 inches and 3 inches.

[0075] The chamber setup of block 512 may also need to take into accountthe arrangement of an array of substrates on the platform that are beingplasma plated. For example, a filament that is positioned in the vacuumchamber so that it will provide a dispersion pattern to providedepositant coverage to inwardly facing surfaces of an array ofsubstrates, it may require anywhere from 20 to 80 percent less mass orweight of depositant when compared with a filament positioned in thevacuum chamber to provide coverage for the array of outwardly facingsurfaces. The reference to inwardly and outwardly are relative to theplatform or turntable with inwardly referring to those surfaces closerto the center of the platform or turntable. This is because theefficiency of the plasma plating process is greater for the inwardlyfacing surfaces of an array of substrates than at the outwardly facingsurfaces of the array of substrates because of the forces attractingthe, generally, positive ions of the plasma. This also ensures that thethickness of the deposition layer on the inwardly facing surfaces andthe outwardly facing surfaces are more uniform. In such a case, theweight or mass of the depositant will, preferably, need to vary betweensuch filament positions. Generally, the variance in mass or weightbetween the two locations may be anywhere from 20 to 80 percentdifferent. Preferably, the depositants in the filaments covering theinwardly facing surfaces will use 40 to 50 percent less mass or weightthan the depositants of the filaments covering the outwardly facingsurfaces. The amount of the depositant placed in the filamentscorresponds to the desired thickness of the deposition layer, and anysublayers thereof. This was discussed more fully and is illustrated morefully in connection with FIG. 3.

[0076] The type of filament affects the dispersion pattern achievedthrough the melting or evaporation of its depositant during the creationof the plasma. Any of a variety of filament types, shapes, andconfigurations may be used in the present invention. For example, thefilament may be provided as a tungsten basket, a boat, a coil, acrucible, a ray gun, an electron beam gun, a heat gun, or as any otherstructure, such as a support structure provided within the vacuumchamber. The filaments are generally heated through the application ofan electric current through the filament. However, any method or meansof heating the depositant within the filament may be used in the presentinvention.

[0077] The setup of the vacuum chamber also includes placing thedepositants in the one or more filaments. The present inventioncontemplates the use of virtually any material that is capable of beingevaporated under the conditions and parameters of the present inventionso that a plasma will form. For example, the depositant may includevirtually any metal, such as a metal alloy, gold, titanium, chromium,nickel, silver, tin, indium, lead, copper, palladium, silver/palladiumand any of a variety of others. Similarly, the depositant may includeany other materials such as carbon, nonmetals, ceramics, metal carbides,metal nitrates, and any of a variety of other materials. The depositantswill generally be provided in a pellet, granule, particle, powder, wire,ribbon, or strip form. Once the filaments have been properly positionedand loaded, the vacuum chamber may be closed and sealed. This mayinclude sealing the bell portion of the vacuum chamber with its baseplate.

[0078] The method 500 proceeds next to block 514 where preparations aremade to begin establishing a vacuum condition within the vacuum chamber.In one embodiment, such as the system 10 shown in FIG. 1, a roughingpump is started to begin evacuating the vacuum chamber and to bring thepressure down within the vacuum chamber to a sufficient level so thatadditional pumps may take over to further reduce the pressure within thevacuum chamber. In one embodiment, the roughing vacuum pump is amechanical pump that may be started, and a roughing valve may then beopened to provide access to the vacuum chamber. Once the roughing vacuumpump has achieved its desired function and has reduced the pressure inthe vacuum chamber to its desired or designed level, the roughing valveis shut. At this point, the method 500 transitions to block 516.

[0079] At block 516, the pressure within the vacuum chamber is furtherreduced using another vacuum pump. For example, in one embodiment, adiffusion pump/foreline pump is utilized to further reduce the pressurewithin the vacuum chamber. In the embodiment of the present invention asillustrated in FIG. 1, this is achieved by opening the main valve andallowing the diffusion pump, supported by the mechanical foreline pump,to further pull or reduce the pressure in the vacuum chamber.

[0080] Generally, the pressure in the vacuum chamber is reduced to alevel that is at or below 4 milliTorr. Preferably, the pressure in thevacuum chamber is reduced to a level that is at or below 1.5 milliTorr.In the event that backsputtering, which is described below in connectionwith block 518 of the method 500, is to be performed, the pressure inthe vacuum chamber is reduced to a level below 100 milliTorr andgenerally in a range between 20 milliTorr and 100 milliTorr. In apreferred embodiment when backsputtering is to be performed, thepressure is reduced in the vacuum chamber at a level below 50 milliTorr,and generally at a level between 20 milliTorr and 50 milliTorr.

[0081] Preceding next to block 518, a backsputtering process may beperformed to further clean and prepare the substrate. It should beunderstood, however, that such a process is not mandatory. Thebacksputtering process is described in more detail below in connectionwith FIG. 6. The backsputtering process may include the rotation of theplatform or turntable within the vacuum chamber. In such a case, theturntable will generally be rotated at a rate at or between 5revolutions per minute and 30 revolutions per minute. Preferably, theturntable will be rotated at a rate between 12 revolutions per minuteand 15 revolutions per minute. The operation of the turntable, whichalso will preferably be used as the deposition layer is being formed onthe substrate according to the teachings of the present invention.

[0082] Method 500 proceeds next to block 520 where an operating vacuumis established. Although a vacuum condition has already been establishedwithin the vacuum chamber, as previously discussed in connection withblock 514 and 516, an operating vacuum can now be established throughthe introduction of a gas into the vacuum chamber at a flow rate thatwill raise the pressure in the vacuum chamber to a level generally at orbetween 0.1 milliTorr and 4 milliTorr. Preferably, the introduction ofthe gas is used to raise the pressure in the vacuum chamber to a levelthat is at or between 0.5 milliTorr and 1.5 milliTorr. This will ensurethat there are no depositant ion collisions within the plasma, whichwill increase the depositant efficiency and provide a clean, highlyadhered deposition layer to the substrate. The gas that is introducedinto the vacuum chamber may be any of a variety of gases but willpreferably be provided as an inert gas, a noble gas, a reactive gas or agas such as argon, xenon, radon, helium, neon, krypton, oxygen,nitrogen, and a variety of other gases. It is desirable that the gas isa noncombustible gas. It should be understood that the present inventiondoes not require the introduction of a gas but may be performed in theabsence of a gas.

[0083] At block 522, various operating parameters and values of thesystem are established. This will generally include the rotation of aturntable, if desired, the application of a dc signal, and theapplication of a radio frequency signal. Assuming that the platformincludes a turntable or some other rotating device, the turntablerotation will preferably be established at this point. This assumes, ofcourse, that the rotation of the turntable was not previously startedand the discretionary backsputtering block 518. Once the rotation of theturntable has been established, the dc signal and the rf signal may beapplied to the substrate. The application of the dc signal to thesubstrate will generally be provided at a voltage amplitude that is ator between one volt and 5,000 volts. Note that the polarity of thevoltage will preferably be negative; however, this is not alwaysrequired. In a preferred embodiment, the application of the dc signal tothe substrate will be provided at a voltage level at or between negative500 volts and negative 750 volts.

[0084] The application of the radio frequency signal to the substratewill generally be provided at a power level that is at or between 1 wattand 50 watts. Preferably, the power level of the radio frequency signalwill be provided at 10 watts or between a range defined by 5 watts and15 watts. The frequency of the radio frequency signal will generally beprovided at an industrial specified frequency value in either thekilohertz range or the megahertz range. Preferably, the frequency signalwill be provided at a frequency of 13.56 kilohertz. Although the termradio frequency has been used throughout to describe the generation andapplication of the radio frequency signal to the substrate, it should beunderstood that the term radio frequency should not be limited to itscommonly understood definition of signals having frequencies roughlybetween 10 kilohertz and 100,000 megahertz. The term radio frequencyshall also include any signal with a frequency component that isoperable or capable of assisting with the creation or excitation of aplasma in a vacuum chamber.

[0085] Block 522 will also preferably include the mixing of the dcsignal and the radio frequency signal, using mixer circuitry, togenerate a mixed signal. This allows only one signal to be applied tothe substrate. This is generally achieved using the electrical feedthrough that extends through the base plate of the vacuum chamber andcontacts an electrically conductive portion of the platform, which inturn electrically couples to the substrate or substrates. Block 522 mayalso include the balancing of the mixed signal through the use of aradio frequency balancing network. Preferably, the mixed signal isbalanced by minimizing the standing wave reflected power. This ispreferably controlled through a manual control.

[0086] As the output or load characteristics of the antenna or outputchanges, as seen from the mixer circuitry, problems can arise whenelectrical signals or waves are reflected from the output load back tothe mixer or source. These problems may include damage to the radiofrequency transmitter and a reduction in the transfer of power to thesubstrate and vacuum chamber to ensure the formation of a sufficientplasma to achieve a successful plasma plating process.

[0087] This problem can be reduced or solved by including the radiofrequency balancing network that can adjust its impedance, including inone embodiment its resistance, inductance, and capacitance, to match orreduce the presence of reflected waves. The impedance and electricalcharacteristics of the output load or antenna are affected by suchthings as the presence and/or absence of a plasma and the shape andproperties of the substrate or substrates on the platform. Because ofsuch changes during the plasma plating process, the radio frequencybalancing network may need to be adjusted during the process to minimizethe standing wave reflected power or, stated differently, to prevent orreduce the standing wave ratio return to the radio frequencytransmitter. Preferably, these adjustments are performed manually by anoperator during the plasma plating process. In other embodiments, theradio frequency balancing network is automatically adjusted. Care mustbe taken, however, to ensure that the automatic adjustment does not overcompensate or poorly track the changes in the output load.

[0088] The method 500 proceeds next to block 524 where the depositant ordepositants are melted or evaporated so that a plasma will be generated.The generation of the plasma at the conditions provided by the presentinvention will result in a deposition layer being formed on the surfaceof the substrate through plasma plating. It is believed that thedeposition layer is formed at a medium energy level on the average ofbetween 10 eV and 90 eV.

[0089] The depositants are generally evaporated or vaporized byproviding a current through the filament around the depositant. In apreferred embodiment, the depositants are slowly or incrementally heatedto achieve a more even heat distribution in the depositant. This alsoimproves the formation of the plasma. The current may be provided as analternating current or as any other current that is sufficient togenerate heat in the filament that will melt the depositant. In otherembodiments, the depositant may be heated through the introduction of anagent that is in chemical contact with the depositant. In still otherembodiments, the depositant may be heated through the use ofelectromagnetic or microwave energy.

[0090] The conditions in the vacuum chamber will be correct for theformation of a plasma. The plasma will generally include gas ions, suchas argon ions, and depositant ions, such as gold, nickel, or palladiumions. The gas ions and the depositant ions will generally be provided aspositive ions due to the absence of one or more electrons. The creationof the plasma is believed to be assisted through the introduction of theradio frequency signal and because of thermionic phenomena due to theheating of the depositants. It is contemplated that in some situations,a plasma may be generated that includes negatively charged ions.

[0091] The negative potential established at the substrate due to the dcsignal will attract the positive ions of the plasma. Once again, thiswill primarily include depositant ions and may include gas ions, such asargon gas ions from the gas that was introduced earlier in method 500.The inclusion of the gas ions, such as argon ions, are not believed todegrade the material or mechanical characteristics of the depositionlayer.

[0092] It should be noted that some prior literature has suggested thatthe introduction of a magnet at or near the substrate is desirable toinfluence the path of the ions of the plasma as they are attracted tothe substrate to form the deposition layer. Experimental evidence nowsuggests that the introduction of such a magnet is actually undesirableand produced unwanted effects. The presence of the magnet may lead touneven deposition thicknesses, and prevent or significantly impede thecontrollability, repeatability, and reliability of the process.

[0093] Whenever the deposition layer is designed to include multiplesublayers, multiple shots must be performed at block 524. This meansthat once the base layer depositants have been melted through theheating of their filaments, the transition layer depositants (or thedepositant of the next layer to be applied) are heated and melted by theintroduction of heat at their filaments. In this manner, any number ofsublayers may be added to the deposition layer. Before successivedepositant sublayers are formed, the preceding layer shall have beenfully or almost fully formed. The method 500 thus provides thesignificant advantage of allowing a deposition layer to be createdthrough multiple sublayers without having to break vacuum andreestablish vacuum in the vacuum chamber. This can significantly cutoverall plasma plating time and costs.

[0094] The method 500 proceeds next to block 526 where the process orsystem is shut down. In the embodiment of the system shown in FIG. 1,the main valve is closed and a vent valve to the vacuum chamber isopened to equalize pressure inside the vacuum chamber. The vacuumchamber may then be opened and the substrate items may be immediatelyremoved. This is because the method 500 does not generate excessive heatin the substrates during the plasma plating process. This providessignificant advantages because the material or mechanical structure ofthe substrate and deposition layer are not adversely affected byexcessive temperature. The plasma plated substrates may then be used asneeded. Because the temperature of the substrates are generally at atemperature at or below 125 Fahrenheit, the substrates can generally beimmediately handled without any thermal protection.

[0095] The method 500 provides the additional benefit of not generatingany waste byproducts and is environmentally safe. Further, the method500 is an efficient process that efficiently uses the depositants suchthat expensive or precious metals, such as gold and silver, areefficiently utilized and are not wasted. Further, due to the fact thatthe present invention does not use high energy deposition techniques, noadverse metallurgical or mechanical effects are done to the substrate.This is believed to be due to the fact that the deposition layer of thepresent invention is not deeply embedded within the substrate, butexcellent adherence, mechanical, and material properties are stillexhibited by the deposition layer. After the substrates have beenremoved at block 528, the method 500 ends at block 530.

[0096]FIG. 6 is a flow chart of a method 600 for backsputtering usingthe system and method of the present invention, according to anembodiment of the present invention. As mentioned previously,backsputtering may be used to further clean the substrate before adeposition layer is formed on the substrate through plasma plating.Backsputtering generally removes contaminants and foreign materials.This results in a cleaner substrate which results in a stronger and moreuniform deposition layer. The method 600 begins at block 602 andproceeds to block 604 where a gas is introduced into the vacuum chamberat a rate that maintains or produces a desired pressure within thevacuum chamber. This is similar to what was previously described inblock 520 in connection with FIG. 5. Generally, the pressure in thevacuum chamber should be at a level at or below 100 milliTorr, such asat a range between 20 milliTorr and 100 milliTorr. Preferably, thepressure is provided at a level at or between 30 milliTorr and 50milliTorr.

[0097] The method 600 proceeds next to block 606 where rotation of theplatform or turntable is established, if applicable. As mentionedpreviously, the rotation of the turntable may be provided at a ratebetween 5 revolutions per minute and 30 revolutions per minute but ispreferably provided at a rate between 12 revolutions per minute and 15revolutions per minute.

[0098] Proceeding next to block 608, a dc signal is established and isapplied to the substrate. The dc signal will generally be provided at anamplitude at or between one volt and 4,000 volts. Preferably, the dcsignal will be provided at a voltage between negative 100 volts andnegative 250 volts.

[0099] Block 608 also involves the generation of a radio frequencysignal that will be applied to the substrate. The radio frequency signalwill generally be provided at a power level at or between 1 watt and 50watts. Preferably, the radio frequency signal will be provided at apower level of 10 watts or at or between 5 and 15 watts. The dc signaland the radio frequency signal are preferably mixed, balanced, andapplied to the substrate as a mixed signal. As a consequence, a plasmawill form from the gas that was introduced at block 604. This gas willgenerally be an inert gas or noble gas such as argon. The formation ofthe plasma includes positive ions from the gas. These positive ions ofthe plasma will be attracted and accelerated to the substrate, whichwill preferably be provided at a negative potential. This results incontaminants being scrubbed or removed from the substrate. Once thecontaminants or foreign matter are removed from the substrate, they aresucked out of the vacuum chamber through the operation of the vacuumpump, such as the diffusion pump.

[0100] Proceeding next to block 610, the backsputtering processcontinues for a period of time that is generally between 30 seconds andone minute. Depending on the condition and cleanliness of the substrate,the backsputtering process may continue for more or less time.Generally, the backsputtering process is allowed to continue until thecapacitance discharge, created by the backsputtering process issubstantially complete or is significantly reduced. This may be visuallymonitored through the observation of sparks or light bursts thatcoincide with the capacitive discharge from the contaminants from thesubstrate. This may be referred to as microarcing.

[0101] During the backsputtering process, the dc signal must becontrolled. This is normally achieved through manual adjustments of a dcpower supply. Preferably, the voltage of the dc signal is provided at alevel that allows the voltage to be maximized without overloading the dcpower supply. As the backsputtering process continues, the current inthe dc power supply will vary because of changes in the plasma thatoccur during the backsputtering process. This makes it necessary toadjust the voltage level of the dc signal during the backsputteringprocess.

[0102] The method 600 proceeds next to block 612 where the dc signal andthe radio frequency signal are removed and the gas is shut off. Themethod 600 proceeds next to block 614 where the method ends.

[0103]FIG. 7 is a top view of a mobile plating system 700 according toone embodiment of the present invention. The mobile plating system 700is implemented using a mobile storage volume 702. In a preferredembodiment, the mobile storage volume 702 is a enclosed or semi-enclosedtrailer commonly used and pulled by a diesel truck, such as a “semi” or“18 wheeler.” It should be understood, however, that the mobile storagevolume 702 of the present invention may be implemented using virtuallyany available mobile storage volume, cargo box, trailer, or the likesuch as, for example, a cargo box, a SEA/LAND cargo box, the internalstorage volume of a truck-trailer or tractor-trailer, a semi-trailer, afreight van, a refrigerated van, a freight trailer, a reefer, a platformtrailer, a dump trailer, a tractor-trailer, or an enclosed deck trailer.Although the preferred embodiment of the mobile storage volume 702 isthat of an enclosed or semi-enclosed volume, the present invention is solimited, and could, in another embodiment, be implemented in an open orsemi-open trailer or cargo box.

[0104] The mobile plating system 700 is shown with an external vacuumpump 704 positioned external to the mobile storage volume 702. Thisillustrates the situation where the mobile plating system 700 isstationary and operational. When the mobile plating system 700 is intransit or not in an operational mode, the external vacuum pump 704 maybe stored within the mobile storage volume 702. For example, an accessdoor 706 is shown near the external vacuum pump 704, and, in a preferredembodiment, the external vacuum pump 704 may be stored with the mobilestorage volume 702 using the access door 706. The external vacuum pump704 would then reside with the mobile storage volume 702 during transit.The present invention should not be limited to any location or existenceof any access door, such as the access door 706 or an access door 754,which also provides access to the mobile storage volume 702. In apreferred embodiment, the external vacuum pump 704 includes a mechanicalroughing pump 708 and a mechanical foreline pump 710 mounted to a skid.In this manner, the external vacuum pump 704 may be conveniently andquickly moved to and from the mobile storage volume 702 through theaccess door 706. For example, the external vacuum pump 704 may be movedto and from the mobile storage volume 702 using a forklift.

[0105] The placement and operation of the external vacuum pump 704external to the mobile storage volume 702 provides the significanttechnical advantage of reducing or eliminating internal vibration,noise, and leaks that could arise within the equipment and systemsprovided in the mobile storage volume 702 during the plating process.These types of vibrations and mechanical strain can dramatically harmthe overall plating process. In general, the external vacuum pump 704 isprovided to assist with producing a desired pressure within a vacuumchamber 712, which is positioned within the mobile storage volume 702,so that the desired plating process may take place under desired andreliable operating parameters. In a preferred embodiment, the roughingpump 708 couples with the vacuum chamber 712 through or using a flexiblepiping segment 714. Similarly, the foreline pump 710 may couple to orwith the vacuum chamber 712 using a- flexible piping segment 714 and, inthe embodiment shown in FIG. 7, through an internal vacuum pump 716,which is shown implemented as a diffusion pump. The flexible piping 714also assists with eliminating, reducing, or isolating the mechanicalvibration, strain, and noise induced by the external vacuum pump 704 onother equipment, machines, and systems, in addition to the externalvacuum pump 704 being located external to the mobile storage volume 702.In addition, the flexible piping segment 714 allows for the movement ofsuch flexible piping segment so that pipes are not mechanicallystressed, fatigued, and potentially cracked or broken, which wouldrequire a complete shut-down of the mobile plating system 700. Oneembodiment of the interface between the external vacuum pump 704 and thevacuum chamber 712 (and internal vacuum pump 716) are illustrated morefully in the description below in connection with FIG. 8.

[0106] Before proceeding, it should be emphasized that the mobileplating system 700 of the present invention is not limited in any mannerto any particular type of plating process, system, or depositiontechnology. As was described in detail above in connection with FIGS.1-6, a plasma plating system or process may be implemented using themobile plating system 700. The present invention may utilize virtuallyany known or available plating process that uses a vacuum chamber and avacuum pump. For example, and without limitation, the mobile platingsystem 700 may use any of the following plating processes: vacuumdeposition, physical vapor deposition, chemical vapor deposition,sputtering, ion plating, and ion implantation. In essence, the mobileplating system 700 that is illustrated in FIG. 7 reflects animplementation of the plasma plating system 10 that has been describedabove in connection with FIG. 1.

[0107] The mobile storage volume 702 may electrically couple to a sourceof electricity through a transformer 718. The transformer 718 may thenprovide the appropriate, desired, or required voltages and power neededby the various equipment and systems of the mobile plating system 700.In one embodiment, not illustrated in FIG. 7, an electrical bus may beprovided near the ceiling of the mobile storage volume 702 so that theelectrical source is conveniently available throughout the mobilestorage volume 702 but is positioned in such a manner that it is not asafety hazard. An air conditioner 720 is also shown in FIG. 7. The airconditioner 720 functions to provide a suitable and comfortable workingenvironment within the mobile storage volume 702 and assist with coolingany equipment that needs cooling.

[0108] A cooling system is shown within the mobile storage volume 702that includes a chiller 722, a water tank 724 and appropriate plumbingor coupling so that chilled or cooled water may be provided from thechiller 722 to the internal vacuum pump 716, which is shown implementedas a diffusion pump, where heat is exchanged between the cooled waterand the internal vacuum pump 716 and the water is then provided back tothe water tank 724, where it can later be provided to the chiller 722for cooling. Although this was not shown in the system 10 of FIG. 1, theinternal vacuum pump 716, similar to the diffusion pump 42 of FIG. 1,requires a cooling system to operate appropriately to ensure thatoperating pressures within the vacuum chamber 712 are generated andmaintained as required by the particular plating process. The chiller722 may be implemented using a refrigeration unit such that hot exhaustair generated by the refrigeration unit may be vented from within theinterior of the mobile storage volume 702 through a duct 726.

[0109] The mobile plating system 700 of the present invention alsoprovides the significant advantage of allowing very large, bulky, andheavy components to be handled with relative ease. The substrate, part,or component to be coated or plated is received at the main access pointof the mobile storage volume 702, which is located and created when amain access door 728 and a main access door 730 are opened, as isillustrated in FIG. 7. In the situation where the substrate isespecially heavy or cumbersome, a trolley/hoist assembly 732 is providednear the main access point or opening. In the embodiment shown, thetrolley/hoist 732 includes a frame structure mounted near the ceiling ofthe mobile storage volume 702. The frame structure of the trolley/hoist732 is moveable and is powered through a motor 734. The motor 734 allowsthe trolley/hoist 732 to roll or slide into or out of the main openingof the mobile storage volume 702 on or along railings positioned nearthe ceiling or upper portion of the mobile storage volume 702 usingwheels, such as a wheel 736 as illustrated. In a preferred embodiment,the mobile plating system 700 includes railing extensions 738 and 740(which may also be referred to as “trolley-wings”) that are hingeablymounted such that the railing extensions 738 may be positioned to extendthe railings mentioned above for the trolley/hoist 732 to extend outsideof the mobile storage volume 702.

[0110] As is indicated by the double arrow, the trolley/hoist 732 maymove within and out of the mobile storage volume 702. When thetrolley/hoist 732 is moved out of the mobile storage volume 702, therailing extension 738 and 740 provide the rail in which the variouswheels, such as the wheel 736, of the trolley/hoist 732 may ride or rollupon.

[0111] In operation, a bulky or cumbersome piece is provided at theoutside of the main opening or access point of the mobile storage volume702. The trolley/hoist 732 is then moved, using the motor 734 such thatthe hoist (not specifically shown in FIG. 7) of the trolley/hoist 732 ispositioned over or near the bulky substrate. As explained previously,the rolling extension 738 and 740 are used to support the trolley/hoist732 as it is provided outside the mobile storage volume 702 of themobile plating system 700. The hoist, which is preferably provided as anelectrical or motorized hoist, is then lowered and the substrate israised to an appropriate level. The trolley/hoist 732 is then positionedto within the main opening of the mobile storage volume 702 until thesubstrate is provided at a desired position.

[0112] The desired position of the substrate will, preferably, beprovided generally over a moveable cart or platform 742. The substrateis then placed on the moveable cart or platform 742 by lowering thesubstrate using the hoist of the trolley/hoist 732. The moveable cart orplatform 742, in the preferred embodiment as shown in FIG. 7, may beprovided on tracks 744. This allows the substrate to be moved to thevacuum chamber 712 using the moveable cart or platform 742 over thetracks 744. A table or platform may be positioned on top of the moveablecart or platform 742 and will, preferably, be provided so that thesubstrate rests upon this surface. This table or platform and thesubstrate may then be positioned within the vacuum chamber 712 suchthat, in one embodiment, the table or platform, with the substrate onits surface, is slid into the vacuum chamber 712 along railings providedwithin the sides of the vacuum chamber 712. The vacuum chamber 712 isillustrated, in the embodiment of FIG. 7, as a large metal vessel with alarge door opening nearest the tracks 744. The vacuum chamber 712 may beprovided in any of a variety of known or available configurations andmaterials.

[0113] Now that the bulky or cumbersome substrate (or any othersubstrate for that matter) is provided within the vacuum chamber 712,the plating process may proceed as desired. For example, the platingprocess may utilize the method for plasma plating, as discussed above inconnection with FIG. 5. In such a case, the appropriate operationalparameters are established using all of the equipment previouslydescribed in connection with FIG. 1.

[0114] Generally, a control module 746 is used to control all or some ofthe various vacuum pumps, valves, and other associated equipment, suchas associated equipment 748, needed to perform and monitor the platingprocess. The associated equipment 748 may include, in one embodiment,equipment similar to what is shown in FIG. 1. For example, theassociated equipment 748 may include a dc power supply operable togenerate a desired voltage at the substrate, similar to the dc powersupply 66 of FIG. 1, an rf transmitter operable to generate an rf signalat a desired power level at the substrate, similar to the rf transmitter64 of FIG. 1, a filament power control module operable to generate acurrent at a desired level at a filament within the vacuum chamber 712.The control module 746 may also provide the controls for theintroduction of a gas into the vacuum chamber 712 such as argon gas 750.The control module 746 may also control a motor 752, which is used toprovide mechanical energy within the vacuum chamber 712 such as formechanical energy to rotate a turntable or rollers on the platform inwhich the substrate rests. This is similar to the drive motor 24 of FIG.1.

[0115] In still other embodiments, the mobile plating system 700 mayinclude a bead blast cabinet within the mobile storage volume 702. Thebead blast cabinet, which is not shown in FIG. 7, may be used to clean asubstrate before introducing the substrate into the vacuum chamber 712for plating.

[0116]FIG. 8 is a side view of a connection of the external vacuum pump704 to the vacuum chamber 712 of the mobile plating system 700,according to one embodiment of the present invention. The externalvacuum pump 704 includes the roughing pump 708 and the foreline pump710. Both the roughing pump 708 and the foreline pump 710 are shown withboth a pump and a motor and are shown mounted on a skid 780. In apreferred embodiment, the skid 780 is operable to be lifted with aforklift.

[0117] The roughing pump 708 couples to the vacuum chamber 712 throughpiping that includes a roughing isolation valve 782, a flexible pipingsegment 784 that extends through or to a disconnect box 786 at themobile storage volume 702 to within the mobile storage volume 702.Within the mobile storage volume 702, the coupling between the roughingpump 708 and the vacuum chamber 712 further includes a flexible pipingsegment 788, and a roughing valve 790 before coupling directly to thevacuum chamber 712.

[0118] The coupling between the foreline pump 710 of the external vacuumpump 704 to the diffusion pump of internal vacuum pump 716 and then tothe vacuum chamber 712 includes various piping elements similar to whatwas just described with respect to the roughing pump 708. This couplingor connection includes a flexible piping segment 792, which couples topiping that connects with the disconnect box 786 to extend within themobile storage volume 702, a flexible piping segment 794 and a forelinevalve 796 before coupling directly with the diffusion pump 716. Thediffusion pump 716 then couples with the vacuum chamber 712 through amain valve 798.

[0119] A cross-connect valve 800 is shown providing a coupling betweenthe two paths just described. Although the cross-connect valve 800 isnormally closed, in the event that either the mechanical foreline pump710 or the mechanical roughing pump 708 breaks down or requiresmaintenance, the cross-connect valve 800 allows only one of the justdescribed pumps to be used to create the desired vacuum within thevacuum chamber 712. This provides significant flexibility and enhancesoverall operational reliability.

[0120]FIG. 9 is flow chart that illustrates a method 900 for using themobile plating system 700 according to one embodiment of the presentinvention. The method 900 begins at block 902 and proceeds to block 904.At block 904, the mobile plating system is located or positioned at adesired location. For example, in the event that the mobile platingsystem is used at a nuclear power plant, the mobile plating system willbe located at or near the nuclear power plant site so that any criticalparts or components that need to be coated or plated may be convenientlyand easily transported without the fear of any loss shipments or delaysin shipping. At block 906, the external vacuum pump is removed from theinterior or from within the mobile storage volume of the mobile platingsystem and located or positioned external the mobile storage volume.This provides the considerable and significant advantage of eliminatinga tremendous source of mechanical noise and vibration which caninterfere with the plating process.

[0121] The method 900 proceeds next to block 908 where the externalvacuum pump is coupled to the vacuum chamber using the flexible pipingsegments. As just discussed above, this also further isolates theexternal vacuum pump and eliminates potential failures or breakdowns dueto mechanical stresses, cracks, and leaks. Proceeding next to block 910,a substrate, such as a reactor vessel head stud, may be positionedwithin the vacuum chamber along with a depositant. As was discussed inconnection with FIG. 7, in the event that the substrate is a large orbulky component, the present invention provides the significantadvantage of allowing such substrates to be conveniently handled usingthe trolley/hoist, which can extend outside of the mobile storage volumeof the mobile plating system. The substrate can then be positionedprecisely as desired on a platform or table which can then be slid orpositioned within the vacuum chamber.

[0122] The method 900 proceeds next to block 912 where the platingprocess begins. This will generally include establishing a desiredpressure or pressures within the vacuum chamber and establishing desiredoperational parameters within the vacuum chamber. Finally, the method900 proceeds to block 914 where the substrate is plated with adepositant using virtually any known or available plating or depositiontechnology such as vacuum deposition, plasma plating, physical vapordeposition, chemical vapor deposition, ion plating, sputtering, and ionimplantation. Finally, the method 900 ends at block 916.

[0123] Thus, it is apparent that there has been provided, in accordancewith the present invention, a mobile plating system and method thatsatisfies one or more of the advantages set forth above. Although thepreferred embodiment has been described in detail, it should beunderstood that various changes, substitutions, and alterations can bemade herein without departing from the scope of the present invention,even if all, one, or some of the advantages identified above are notpresent. For example, the vacuum chamber and the external vacuum pumpmay be coupled using one or more flexible piping segments or joints, andmay be coupled through an internal vacuum pump, such as, for example, adiffusion vacuum pump, cryo pump and/or a turbo molecular pump. Thepresent invention may be implemented using any of a variety of materialsand configurations. For example, any of a variety of vacuum pumpsystems, equipment, and technology could be used in the presentinvention. These are only a few of the examples of other arrangements orconfigurations of the mobile plating system and method that iscontemplated and covered by the present invention.

[0124] The various components, equipment, substances, elements, andprocesses described and illustrated in the preferred embodiment asdiscrete or separate may be combined or integrated with other elementsand processes without departing from the scope of the present invention.For example, one of more pumps may be coupled or integrated to assistwith providing or maintaining a designated pressure or vacuum conditionin a vacuum chamber. Other examples of changes, substitutions, andalterations are readily ascertainable by one skilled in the art andcould be made without departing from the spirit and scope of the presentinvention.

What is claimed is:
 1. A mobile plating system for performing a platingprocess, the mobile plating system comprising: a mobile storage volume;a vacuum chamber positioned in the mobile storage volume, the vacuumchamber having an internal volume large enough to contain a substrate tobe plated that is the size of at least one reactor vessel head stud; anexternal vacuum pump operable to be positioned within the mobile storagevolume when the mobile plating system is in transit, and to operateexternal the mobile storage volume when the mobile plating system isstationary and in operation, the external vacuum pump operable to assistwith producing a desired pressure in the vacuum chamber when the mobileplating system is stationary and in operation, and to couple with thevacuum chamber through a coupling that reduces at least some of thevibrations created by the operation of the external vacuum pump frombeing transmitted to the vacuum chamber; a control circuitry operable tocontrol the external vacuum pump; a support structure operable to bepositioned within the vacuum chamber and to support the substrate to beplated; and a filament operable to hold a depositant within the vacuumchamber in relation to the support structure.
 2. The mobile platingsystem of claim 1, further comprising: an associated equipment thatincludes: a dc power supply operable to generate a desired voltage atthe substrate, an rf transmitter operable to generate an rf signal at adesired power level at the substrate, and a filament power controlmodule operable to generate a current at a desired level at thefilament.
 3. The mobile plating system of claim 1, wherein the mobilestorage volume is a trailer.
 4. The mobile plating system of claim 1,wherein the mobile storage volume is a cargo box.
 5. The mobile platingsystem of claim 4, wherein the cargo box is a SEA/LAND cargo box.
 6. Themobile plating system of claim 1, wherein the mobile storage volume is acargo volume of a truck.
 7. The mobile plating system of claim 1,wherein the external vacuum pump is mounted on a skid.
 8. The mobileplating system of claim 1, wherein the external vacuum pump is amechanical pump.
 9. The mobile plating system of claim 1, wherein theexternal vacuum pump is a roughing pump.
 10. The mobile plating systemof claim 1, wherein the external vacuum pump includes a roughing pumpand a foreline pump.
 11. The mobile plating system of claim 10, whereinthe roughing pump is a mechanical pump that couples with the vacuumchamber using a first flexible piping segment, and the foreline pump isa mechanical pump that couples with the vacuum chamber through a secondflexible piping segment.
 12. The mobile plating system of claim 1,further comprising: an internal vacuum pump operable to couple with thevacuum chamber to assist with producing the desired pressure in thevacuum chamber.
 13. The mobile plating system of claim 12, wherein thecontrol circuitry is operable to control the internal vacuum pump. 14.The mobile plating system of claim 12, wherein the internal vacuum pumpis a diffusion pump.
 15. The mobile plating system of claim 12, furthercomprising: a cooling system operable to cool the internal vacuum pump.16. The mobile plating system of claim 2, wherein the control circuitryis operable to control the dc power supply, the rf transmitter, and thefilament power control module.
 17. The mobile plating system of claim 1,wherein the support structure is operable to rotate the substrate andfurther comprising: a motor operable to control the rotation of thesupport structure, and wherein the control circuitry is operable tocontrol the motor.
 18. The mobile plating system of claim 1, wherein thecontrol circuitry is integrated into one control module.
 19. A mobileplating system for performing a plating process, the mobile platingsystem comprising: a mobile storage volume; a vacuum chamber positionedin the mobile storage volume, the vacuum chamber having an internalvolume large enough to contain a substrate to be plated; an externalvacuum pump operable to be positioned within the mobile storage volumewhen the mobile plating system is in transit, and to operate externalthe mobile storage volume when the mobile plating system is stationaryand in operation, the external vacuum pump operable to assist withproducing a desired pressure in the vacuum chamber when the mobileplating system is stationary and in operation; a means for coupling theexternal vacuum pump to the vacuum chamber to reduce at least some ofthe vibrations created by the operation of the external vacuum pump frombeing transmitted to the vacuum chamber; a control circuitry operable tocontrol the external vacuum pump; a support structure operable to bepositioned within the vacuum chamber and to support the substrate to beplated; and a filament operable to hold a depositant within the vacuumchamber in relation to the support structure.